diff --git a/Source/JavaScriptCore/ChangeLog b/Source/JavaScriptCore/ChangeLog
index b1cd180..b5a10a7 100644
--- a/Source/JavaScriptCore/ChangeLog
+++ b/Source/JavaScriptCore/ChangeLog
@@ -1,3 +1,16 @@
+2019-10-17  Brent Fulgham  <bfulgham@apple.com>
+
+        Build fix for newer versions of MSVC.
+
+        Rubber stamped by Mark Lam.
+
+        Some versions of MSVC optimize the inline optimization of
+        index away, triggering an uninitialized variable error. This
+        change avoids this problem.
+
+        * runtime/Options.cpp:
+        (JSC::optionTypeSpecificIndex):
+
 2019-10-17  Devin Rousso  <drousso@apple.com>
 
         Web Inspector: rework frontend agent construction to allow commands/events to be controlled by the related target's type
diff --git a/Source/JavaScriptCore/runtime/Options.cpp b/Source/JavaScriptCore/runtime/Options.cpp
index 850ee71..29bf1dd 100644
--- a/Source/JavaScriptCore/runtime/Options.cpp
+++ b/Source/JavaScriptCore/runtime/Options.cpp
@@ -291,7 +291,9 @@
 template<OptionTypeID type, OptionID id>
 constexpr size_t optionTypeSpecificIndex()
 {
-    size_t index = 0;
+    size_t index;
+    index = 0; // MSVC (16.3.5) improperly optimizes away the inline initialization of index, so use an explicit assignment.
+
 #define COUNT_INDEX_AND_FIND_MATCH(type_, name_, defaultValue_, availability_, description_) \
     if (id == OptionID::name_) \
         return index; \